High piezoelectricity by multiphase coexisting point: Barium titanate derivatives

BaTiO3-based lead-free piezoelectric materials have long been known as “a mediocre class of piezoelectric materials.” However, they have seen significant renewed interest in recent years ever since the discovery of high piezoelectricity in Ba(Zr, Ti)O3-(Ba, Ca)TiO3 as well as the related Ba(Sn, Ti)O3-(Ba, Ca)TiO3 and Ba(Hf, Ti)O3-(Ba, Ca)TiO3 systems. The unexpectedly high piezoelectricity in this class of BaTiO3 (BT)-based materials is still not well understood and has stimulated significant research activity. We present a concise discussion of the notions leading to high piezoelectricity in BaTiO3-based systems. In particular, the possible role of a multiphase-coexisting point is highlighted